The present invention relates to inkjet printheads in which ink in the liquid state is delivered to a plurality of nozzles and ink drops are ejected on demand from each nozzle in response to actuation of an associated ejection transducer.
Ink jet printers are widely used for printing documents in both the office and the home, as well as for industrial printing applications on a variety of surfaces. Such printers include an ink jet printhead having a plurality of ink ejection chambers, or channels, each containing one or more ink jet ejection orifices, or nozzles. The ejection of ink from each nozzle is controlled by a pattern of pressure pulses.
Each nozzle constitutes the outlet end of an ink delivery channel. The inlet ends of all of the channels communicate with an ink supply volume formed within an ink manifold. As ink is withdrawn from the manifold, it is replaced by fresh ink from a reservoir that is in communication with the manifold. The printhead is designed so that the ink supply volume is always filled with ink.
The pressure pulses for ejecting ink from each nozzle are produced by an associated ink jet ejection transducer. The transducer, in turn, is responsive to electrical drive pulses produced by a print engine.
When a pressure pulse is generated within a channel, one part of the resulting pressure disturbance acts to eject an ink drop from the associated nozzle while another part of the resulting pressure disturbance is propagated in a backward direction through the channel and into the ink supply volume within the manifold. Pressure disturbances which enter the ink supply volume are transmitted acoustically throughout the ink supply volume.
As a result, a time varying manifold pressure, known as crosstalk, will influence the pressure in all of the other channels. This will affect the flow dynamics within all of the channels. In particular, crosstalk can cause variations to occur in the velocity, shape and/or size of the ink drops ejected from the nozzles of the other channels and such variations will have an adverse effect on the quality of the resulting printed material.
It is an object of the present invention to minimize the transmission of pressure disturbances, or crosstalk, between the channels of a printhead of the type described above.
The invention is embodied in an ink jet printhead comprising: a reservoir storing a quantity of printing ink; at least one ink manifold defining an ink supply volume in communication with the reservoir for holding a supply of ink received from the reservoir; and a plurality of individually controlled ink jet delivery channels, each of the channels having an ink drop ejection transducer and an orifice to eject successive ink drops on demand in response to pressure pulses produced by the transducer, and each of the channels being in communication with the ink supply volume for receiving ink from the ink supply volume, wherein the manifold is constructed to give the ink supply volume a large acoustic compliance to minimize propagation of pressure disturbances in the ink supply volume and acoustic signal crosstalk between the channels.
The invention is applicable to any existing type of printhead, including those of the bubble jet type.